1. Field of Invention
The present invention relates to process reactors, and in particular relates to reactors employing process gases and a plasma source.
2. Description of Background Information
Typically, plasma is a collection of charged particles containing approximately equal numbers of positive and negative charge carriers and can be used in certain processing systems which are useful for a wide variety of applications. For example, plasma processing systems are of considerable use in the manufacture and processing of semiconductors, integrated circuits, displays and other electronic devices, both for etching and layer deposition on substrates, such as, for example, semiconductor wafers.
Generally, the basic components of such a system include a plasma chamber enclosing a processing region in which plasma is formed and a pumping region connecting to a vacuum port. Other basic components of such a system generally include a wafer supporting chuck, which is connected to an RF power supply in order to accelerate the plasma ions to strike the wafer surface with a desired energy. This RF power may often produce the process plasma; however, an additional electrode or RF antenna can be used to produce the process plasma. The chuck is normally cylindrical and flat, supporting a 200 to 300 mm, or larger, diameter wafer or other substrate for processing. For efficient use of chamber space, i.e. maximizing gas flow uniformity and minimizing the reactor footprint, process gases are injected above or around the plasma region, and the used gases are removed through an annular passage between the chuck and the sidewall to the vacuum pumping port provided in the lower portion of the vacuum chamber. With a large mass flow rate of processing gases, a large pumping speed for removing the used gases is important to process performance, including factors such as the etch rate, high aspect ratio etch, profile figure, damage and contamination. The gas conductance of the annular region often severely restricts the pumping speed delivered to the processing region.
In addition to the need of larger chamber conductance, the need for higher pumping speed at the process operating pressure range, i.e., 10-100 m Torr, is generally required for high density plasma (HDP) etch systems. Plasma vacuum pump systems have been proposed for the process system to provide the required pumping speed for removal of the effluent gases.
Some plasma duct systems have employed, for example, magnethydrodynamic (MHD) plasma pumps, to move plasma ions and electrons in an E×B drift direction, where an external electric field and magnetic field are perpendicular to each other, and are perpendicular to the direction of plasma flow. In MHD pumps, the magnetic field must be strong enough so the ions are magnetized.